package other.nowcoder.easy;

import java.util.Scanner;

/**
 * @author bruin_du
 * @description 年会抽奖
 * https://www.nowcoder.com/questionTerminal/610e6c0387a0401fb96675f58cda8559
 * @date 2022/6/4 14:32
 **/
public class AnnualGift {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(in.hasNextInt()){
            int n = in.nextInt();
            long a = 0,b = 1,c = 1;
            long count = 2;
            for (int i = 3; i <= n; i++) {
                c = (i - 1) * (a + b);
                a = b;
                b = c;
                count *= i;
            }
            System.out.printf("%.2f%%\n",(double)c / count * 100);
        }
    }
}
